MATAMOROS, Mexico – Investigators have uncovered 13 more bodies in mass graves in the violent northern state of Tamaulipas, where 59 dead were exhumed earlier this week, officilas said Friday. Families and authorities from across Mexico contacted the morgue in search of those who have vanished in the country’s drug-war.

Seventy-two bodies have now been discovered since authorities began chasing reports in late March that gunmen had kidnapped people off of passenger buses headed toward the U.S. border.

Nine of the bodies were discovered in one newly found grave and four in another on Thursday near the city of San Fernando, state Interior Secretary Morelos Canseco said Friday. The total now matches the number of migrants who died in a massacre near that town last August.

Canseco said investigators are searching for yet more graves in the area.

Families came to the morgue in the border city of Matamoros across from Brownsville, Texas, looking for loved ones not seen for a couple of weeks, others a few months — some as long as three years. Canseco said he has heard from officials in the central states of Guanajuato and Queretaro searching for residents who disappeared on buses traveling through Tamaulipas or to U.S. border.

Guanajuato attorney general spokeswoman Susana Montero said 17 missing people rode an Omnibus de Mexico company bus to northern Mexico in March. The bus route and exact date were unknown, but Montero said they were apparently travelling to the United States.

In the western state of Michoacan, the attorney general’s office said it also was working with Tamaulipas to determine if any of the 59 people missing from that state in the last 12 months were killed and buried in northern Mexico.

Canseco told the Milenio television channel that he had yet to hear from other countries, particulary those in Central America, the origin of thousands of migrants who cross Mexico each year on their way to the U.S.

The victims of the August massacre were from from El Salvador, Honduras, Guatemala, Ecuador and Brazil. Survivors said they were killed for refusing to work for the Zetas drug cartel.

Federal security spokesman Alejandro Poire announced Thursday that 14 suspects linked to the killings had been arrested by Wednesday. Those arrests apparently led authorities to the pits.

The suspects belonged to a “criminal cell,” Poire said, but he did not specify which gang they may have belonged to.

State authorities are still not sure about the origin of the victims found in the pits, but suspect at least some had been abducted from buses.

One man waiting Thursday outside the morgue in this border city — who refused to give his name for fear of reprisals — said his uncle and a cousin left their hometown of Ciudad Valles in the central state of San Luis Potosi on March 25. They were traveling by bus to Rio Bravo in Tamaulipas state but haven’t been heard from.

He said they were supposed to arrive in Rio Bravo on March 26 for a two-week job watering sorghum fields.

“They never made it,” he said, adding that he was afraid to say anything else. “Here one is afraid to talk, here we don’t talk about what happens, but we are desperate to know what happened to them.”

Most of those gathering outside the morgue were desperate for a shred of evidence — even for confirmation of their worst fears.

“I just want to know if he is dead or alive so I can have peace,” said Flor Medellin, her eyes watery as she waited with her husband.

Medellin said her 43-year-old brother last checked in with family last September while hauling cattle in neighboring Nuevo Leon state, like Tamaulipas a border state plagued with drug gang violence.

“They never found the cattle or the trailer truck. They found no traces of him,” Medellin, a 41-year-old laundry manager, said.

“It’s really sad what we’re going through,” she added.

Medellin said her brother often drove on a dangerous highway in Tamaulipas connecting Matamoros to the state capital, Ciudad Victoria. It goes through San Fernando, where the clandestine graves were found at a spot about 80 miles (130 kilometers) south of Brownsville, Texas.

“We think he was intercepted and that they stole everything from him and we don’t know what happened after that. One always has hope that he is alive, but all we want is to know what happened to him,” said Medellin’s husband, Felipe Valadez.

By Thursday, investigators had identified a few victims of the latest killings as Mexicans, not transnational migrants. They did not say if they were connected to 12 official missing-person reports from the buses.

Authorities interviewing witnesses on the bus abductions calculated that from 65 to 82 people went missing, Tamaulipas state Interior Secretary Morelos Canseco said.

Although federal authorities launched an offensive in the region in November seeking to regain control of territory from the warring Gulf and Zetas cartels, criminals have become so brazen they apparently kidnapped the bus passengers in a stretch of open desert that locals say lay between two military checkpoints. Mexico’s military would not comment on the location of roadblocks for security reasons.

Authorities speculate the men pulled off the buses fell victim to ever more brutal recruiting efforts to replenish cartel ranks. But one local politician, who didn’t want to be quoted by name for safety reasons, said there were rumors that the Gulf cartel was sending buses of people to fight the Zetas, who control that stretch of road and who began boarding buses in search of their rivals.

Whether the victims found in the pits were innocents caught up in the violence, migrants or drug traffickers executed by rivals, there are many more missing in San Fernando, the politician said, adding “If they keep looking they’ll find more and more mass graves.”